A vacuum heat insulator, which is buried into a wall of a refrigerator or other appliance to form an insulated wall, is produced in the following manner: First, inorganic powder such as pearlite or organic powder such as pulverized powder of hard urethane foam, which is used as a core material, is densely charged into an air-permeable core-material container bag made of kraft paper or other material. Next, the core-material container bag filled with the core material is housed in a bag made of resin film whereon aluminum vapor deposition or metallic foil laminate is applied and which has superior gas-barrier properties, and then air is removed from the bag so that it is made into a vacuum heat insulator. Conventionally, in order to prepare the core-material container bag filled with the core material, powder such as pearlite is weighed and charged into a core-material container bag made of kraft paper or other material, and after sealing the charging inlet, the bag is manually flattened and then pressurized by a press so as to remove air thereform. Thus, the density of the charged core material is increased.
However, the above-mentioned conventional method has the following problems: Since the volume of the powder before being charged into a core-material container bag and pressurized therein is several times as large as that of the powder after pressurized, a quite large core-material container bag needs to be prepared in comparison with the size of the bag after pressurized. This results in a waste of material, and causes wrinkles over the core-material container bag and areas that do not have sufficient core material due to the difference in sizes before and after the pressurization. Further, since it is hard to charge the core material into the core-material container bag uniformly as well as densely by the manual flattening operation, recessed portions and raised portions are inevitably made. Moreover, powder such as pearlite tends to be scattered during charging, thereby contaminating the working space and giving adverse effects to the worker's health.